• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.921-927
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• 1989

One of the most important problems in recent life prediction is to introduce the degradation effects into life prediction procedure. In the present paper, the effect of the material degradation on the fatigue surface crack growth and fatigue life prediction in a 2 1/4 Cr-1Mo steel were investigated. The 2 1/4 Cr-1Mo steel has been used in a plant having operated for over 60000hours and subjected to material degradation due to temper-embitterment. A Monte-Carlo simulation was made on the basis of the data obtained in the experiment in order to determine the P-S-N diagrams of surface crack growth for the degraded and recovered steels.

• Journal of dental hygiene science
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• v.14 no.1
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• pp.29-34
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• 2014

The purpose of this study was to evaluate the influence of low temperature degradation (LTD) on the bonding strength of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). The push-shear bond test method was used to investigate the core-veneer bonding strength of industrially manufactured Y-TZP core ceramic and manufacturer recommended veneering ceramic. Four groups from ceramic-zirconia specimens (n=28; n=7 per group) were assigned into four experimental aging conditions, namely storage in an autoclave at $134^{\circ}C$ for 0, 3, 5, 10 hours. Bonding strength was obtained using a universal testing machine with crosshead speed 0.5 mm/min. Data were statistically analyzed using one-way ANOVA and Tukey's test (${\alpha}=0.05$). In bonding strength test, the group which was treated with LTD showed lower bonding strength than no treated group. The ceramic-zirconia bonding strength was affected by LTD (p<0.05). Digital microscope examination of the fracture surface showed mixed failures with adhesive and cohesive types in LTD with treated Y-TZP groups.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.3
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• pp.248-253
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• 2014

Camera calibration is an indispensable process for improving measurement accuracy in industry fields such as machine vision. However, existing calibration cannot be applied to the calibration of mid-wave and long-wave infrared cameras. Recently, with the growing use of infrared thermal cameras that can measure defects from thermal properties, development of an applicable calibration target has become necessary. Thus, based on heat conduction analysis using finite element analysis, we developed a calibration target that can be used with both existing visible cameras and infrared thermal cameras, by implementing optimal design conditions, with consideration of factors such as thermal conductivity and emissivity, colors and materials. We performed comparative experiments on calibration target images from infrared thermal cameras and visible cameras. The results demonstrated the effectiveness of the proposed calibration target.

• Electrical & Electronic Materials
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• v.4 no.3
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• pp.229-238
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• 1991

본 논문에서는 영상센서를 이용하여 유기절연물질내의 트리 열화현상을 측정할 수 있는 시스템에 관하여 논하였다. 기존의 육안관찰법으로서는 관측하는 것이 매우 어려웠던 트리형상의 변화를 화상처리 기술을 이용하므로서 트리발생 직후부터 관측할 수 있게 되었다. 실험결과, 화상처리장치는 최초로 발생된 트리에서 부터 그 진전상황을 즉각적으로 기록할 수가 있었으며 트리의 신장도, 열화면적 및 연속 화상처리 측면에서 트리의 진전특성을 고찰하였다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.117-123
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• 2006

최근 들어 전통적인 (가속)수명시험으로도 고 신뢰도 제품의 신뢰도 평가가 힘들므로 제품의 성능열화를 관측하여 수명 정보를 추정하는 열화 시험에 대한 관심이 증대되고 있다. 본 논문은 대수정규분포를 따르는 확률계수 열화율 모형 하에서 분포 모수 및 수명분포의 분위수를 추정하는 세 가지 통계적 분석법(근사적, 해석적, 수치적 방법)의 통계적 성능을 비교하였다. 즉, 다양한 수치실험상황 하에서 모형에 포함되는 (측정)오차의 영향을 고려하여 세 방법의 우월성을 조사하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2019.06a
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• pp.89-91
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• 2019

객체 추적 기술은 컴퓨터 비전 분야에서 활발하게 연구되고 있는 분야로, 인간-컴퓨터 상호작용(HCI)이나 로보틱스, 그리고 자율주행 자동차와 같은 곳에 유용하게 사용될 수 있다. 그중에서도 열화상 객체 추적 기술은 빛이 전혀 없는 어두운 밤에도 적용 가능하기 때문에, 감시 시스템이나 사고 현장의 구조 상황, 또는 군사적 응용에 더욱 유용하다. 그러나 일반적으로 열화상 영상은 컬러 영상보다 해상도가 낮고, 객체의 경계가 흐릿하며, 텍스쳐가 거의 없다는 점 때문에 기존 추적 방법들의 성능 저하의 원인이 된다. 이에 본 논문은 기존 Correlation Filter 기반 추적기에 객체성 특징을 함께 이용하여, 열화상 영상에서의 객체 추적 성능을 향상 시키는 방법을 제안하였다. 또한 실험을 통해 기존 방법보다 열화상 영상에서의 객체 추적 성능이 향상된 것을 보였다.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.67-73
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• 2017

An analysis of thermal degradation of epoxy based adhesive performed by thermogravimetry tests are presented in this study. Six different heating rates were employed for the weight change measurements. Based on the data, an Arrhenius type modeling equation was developed by calculating activation energies and proportional constants, and $n^{th}$ polynomial function was adopted to predict the weight change rates. The prediction results by the modeling was compared with the data using the average activation energy. It was found that the activation energy at the each heating rate was not same due to the different degradation kinetics, especially at the high heating rate. To overcome this pitfall, a new approach using exponential function series was introduced and employed. The calculation results showed very good agreements with the test data regardless of the heating rates.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.138-146
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• 2003

This paper deals with the experimental results that apply to a new wire by an artificial flame-maker because it's difficult to directly analyze the characteristic of deterioration by a forest fire. Those results include tension load, extension rate and torsion number for a conductor. In addition, there's been an experiment and analysis about the mechanical characteristics of the wire of ACSR 480$\textrm{mm}^2$ which was removed from Pohang area by a forest fire. Then, the database will be made to predict the state of deteriorated wires by a forest fire using those two data, and data necessary to diagnose the life state of an ACSR wire affected by a forest fire will be given.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.681-687
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• 2008

This study presents a technique to quantitatively measure the corrosion level of a reinforcing bar using infrared thermography system. We found out electric heating method having an important effect on thermal data in previous study. This study purposed an efficient way for grip standardization to reduce constriction resistance problem, and providing reliable thermal data using infrared thermographic method. Using vise type earth clamp, the surface resistance of rebar was smaller than that of traditional plier type earth clamp through temperature-distribution relationship. Also this study contains experiments with toque wrench to improve heating contact problem.

• Korean Journal of Materials Research
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• v.8 no.2
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• pp.99-104
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• 1998

사용중인 중화학 설비의 재료물성의 경년열화적 특성을 평가하기 위하여 기존 실험법의 인장시험편이나 충격시험편을 채취하기는 실제적으로 불가능하다. 인장강도등 인장특성과 비교한 결과 인장강도, 연신율, 항복강도, 종탄성계수와 소형펀치실험의 각 특성과 선형적 관계를 얻을 수 있었다. 또한 경년열화도를 평가하는 두구인 파면천이온도(FATT)와 비교하기 위하여 저온 소형펀치실험을 실시한 결과 충격실험을 통하여 구한 FATT온도와 소형펀치실험의 천이온도 ( $T_{sp}$ )와 일정한 관계가 있음이 밝혀져 사용재의 열화도를 평가할 수 있다.